After battling stage four throat cancer, Michael Douglas finally got the news he was hoping for: "The tumor is gone."

Still, the Oscar-winning actor admits, it was wife Catherine Zeta-Jones that got emotional. "She had a good cry when she heard," he tells PEOPLE. "I can't tell you I was jumping up and clicking my heels. For me, it will probably be two or three months before it will really sink in and feel good."

But as it sinks in, Zeta-Jones adds exclusively to PEOPLE, "We are so grateful for the wonderful care Michael has received and of course for this happy news. It's an incredible way to start the New Year."

The couple and their kids, Dylan, 10, and Carys, 7, celebrated Douglas's clean bill of health at a Manhattan restaurant on January 6. "We dined on oysters and toasted with Shirley Temples," says Douglas. He also indulged in a glass of wine, his first since his diagnosis in August, but he says, "It didn't taste good."

Though drinking and smoking are two of the main causes of throat cancer, Douglas, 66, says he also believes stress and diet could have played a role. Now, he is "going to be eating much more of an organic diet."

Douglas, who lost 32 lbs. after undergoing seven weeks of radiation and chemotherapy, has gained back about 12 lbs. so far. "I'm eating like a pig," he says.

 With reporting by ALEXIS CHIU

For more on Douglas's recovery and his family's reaction, pick up the new issue of PEOPLE, on newsstands Friday